The present application relates to a mutant protein having diaphorase activity. More specifically, the present application relates to a mutant protein having diaphorase activity and having predetermined levels or more of enzyme activity and heat resistance.
Enzymes are biocatalysts for allowing many reactions for the maintenance of life to smoothly proceed under mild conditions in vivo. Enzymes turn over in vivo, are produced in vivo according to need, and express their catalytic functions.
Techniques for making use of enzymes in vitro have already been used practically or studied to achieve practical use. For example, technology for using enzymes has been developed in various technical fields, such as the production of useful materials, the production of energy-related materials, measurement or analysis, environmental conservation, and medical care. In relatively recent years, technologies, such as an enzyme cell (for example, see Japanese Unexamined Patent Application Publication No. 2004-71559), which is a type of fuel cell, an enzyme electrode, and an enzyme sensor (sensor for measurement of a chemical substance using an enzymatic reaction), have been developed.
In general, enzymes are denatured by degrees of heat and pH. Hence, enzymes have low stability in vitro compared with other chemical catalysts such as metal catalysts. Accordingly, when enzymes are used in vitro, it is important to allow the enzymes to more stably work in response to environmental changes and to allow the activity of the enzymes to be maintained.
When an enzyme is used in vitro, a method for artificially modifying the nature and function of the enzyme and a method for producing the environment of the site in which the enzyme functions are employed. With respect to the former method, it is common that the base sequence of a gene encoding a protein is artificially modified, and the modified gene is expressed in an organism such as Escherichia coli to form an artificially mutated protein, and then the mutant protein having the target function and nature is separated by screening (for example, see Japanese Unexamined Patent Application Publication No. 2004-298185).